Diketopyrrolopyrrole pigments

ABSTRACT

Diketopyrrolopyrroles of the formula (I):                  
 
wherein
     R 1 , R 2 , R 3  and R 4  independently of one another are a C 1 –C 4  alkyl radical or a substituted or unsubstituted phenyl radical, wherein the phenyl radical can be substituted by 1, 2, 3 or 4 substituents from the group C 1 –C 4  alkyl, C 1 –C 4  alkoxy, CN, F, Cl, Br, NO 2 , CF 3 , S—C 1 –C 4  alkyl, phenyl or (C 1 –C 2 )alkylenephenyl,
 
with the proviso that at least one of the radicals, R 1 , R 2 , R 3 , or R 4 , is one of the stated substituted or unsubstituted phenyl radicals.

The present invention relates to new 1,4-diketopyrrolo[3,4-c]pyrroles,referred to below as diketopyrrolopyrroles, which constitute valuablepigments, and also to their preparation and use for pigmenting highmolecular mass materials.

EP-A-0 061 426 discloses a process for the bulk coloring of highmolecular mass organic material, characterized by the use of adiketopyrrolopyrrole.

EP-A-0 094 911 discloses a process for preparing diketopyrrolopyrroles.

The use of pigments for coloring high molecular mass organic materialsimposes exacting requirements on the performance properties of thepigments, such as high color strength, effective light fastness andweather fastness, excellent overcoating fastnesses in the case of use incoating systems, low viscosity of the highly pigmented paintconcentrates (millbase) and, particularly in the case of metallicfinishes, high transparency and brilliant colors. In the case of thecoloring of plastics there is a demand for effective dispersibility,which is manifested, for example, in high color strengths. In printingsystems, too, high color strengths are a requirement. The pigments oughtto be useful as universally as possible.

Many of the diketopyrrolopyrroles disclosed in the abovementionedpublications, however, no longer satisfy present-day requirements.

It was therefore an object to find new diketopyrrolopyrrole pigmentswhich in comparison with the existing diketopyrrolopyrrole pigmentspossess superior properties.

It has been found that this object, surprisingly, is achieved by meansof diketopyrrolopyrrole pigments defined below.

The invention provides diketopyrrolopyrroles of the formula (I),

in which

-   R¹, R², R³ and R⁴ independently of one another are a C₁–C₄ alkyl    radical or a substituted or unsubstituted phenyl radical, it being    possible for the phenyl radical to be substituted by 1, 2, 3 or 4    substituents from the group C₁–C₄ alkyl, C₁–C₄ alkoxy, CN, F, Cl,    Br, NO₂, CF₃, S—C₁–C₄ alkyl, phenyl or (C₁–C₂)alkylenephenyl,    with the proviso that at least one of the radicals, R¹, R², R³, or    R⁴, is one of the stated substituted or unsubstituted phenyl    radicals.

The present invention also provides mixtures of two or more, such as 2or 3, diketopyrrolopyrroles of the formula (I).

Preferably R¹, R², R³ and R⁴ independently of one another are methyl,ethyl, phenyl or else phenyl substituted by 1 or 2 substituents from thegroup methyl, ethyl, methoxy, ethoxy, CN, F, Cl, S-methyl, phenyl orbenzyl.

Of particular interest are symmetrical diketopyrrolopyrroles of theformula (I), in which R¹ and R⁴ are identical and R² and R³ areidentical, especially diketopyrrolopyrroles of the formula (I) in whichR¹ and R⁴ are each a methyl or ethyl group and R² and R³ are identicaland are each a phenyl radical which is unsubstituted or substituted by 1or 2 substituents from the group methyl, ethyl, methoxy, ethoxy, F, Cl,NO₂, CF₃, phenyl or benzyl.

The diketopyrrolopyrrole pigments of the invention and the mixturesaccording to the invention can be prepared by reacting a succinicdiester with a nitrile of the formula (II) or (III),

or with a mixture of 2, 3 or 4 different nitrites of the formula (II) or(III), in an organic solvent in the presence of a strong base withsubsequent hydrolysis, where R¹ to R⁴ are as defined above.

The succinic diesters to be used can be dialkyl, diaryl or monoalkylmonoaryl esters and the succinic dialkyl esters and diaryl esters mayalso be asymmetric. Preference is given to using symmetrical succinicdiesters, especially symmetrical succinic dialkyl esters. If the esteris a succinic diaryl ester or succinic monoaryl monoalkyl ester, thenaryl denotes, in particular, phenyl which is unsubstituted orsubstituted by 1, 2 or 3 substituents from the group halogen, such aschloro, C₁–C₆ alkyl, such as methyl, ethyl, isopropyl, tert-butyl ortert-amyl, or C₁–C₆ alkoxy, such as methoxy or ethoxy. Aryl ispreferably unsubstituted phenyl. Where the ester is a succinic dialkylester or succinic monoalkyl monoaryl ester, alkyl can be unbranched,branched or cyclic, preferably branched, and contain preferably 1 to 18,in particular 1 to 12, especially 1 to 8 and with particular preference1 to 5 carbon atoms. Alkyl is preferably sec- or tert-alkyl, such asisopropyl, sec-butyl, tert-butyl, tert-amyl, cyclohexyl, heptyl,2,2-dimethylhexyl, octyl, decyl, dodecyl, tetradecyl or octadecyl, forexample.

Examples of succinic diesters are dimethyl, diethyl, dipropyl, dibutyl,dipentyl, dihexyl, diheptyl, dioctyl, diisopropyl, di-sec-butyl,di-tert-butyl, di-tert-amyl, di[1,1-dimethylbutyl],di[1,1,3,3-tetramethylbutyl], di[1,1-dimethylpentyl],di[1-methyl-1-ethylbutyl], di[1,1-diethylpropyl], diphenyl,di[4-methylphenyl], di[2-methylphenyl], di[4-chlorophenyl],di[2,4-dichlorophenyl], monoethyl monophenyl or dicyclohexyl succinate.

Use is made in particular of symmetrical succinic dialkyl esters inwhich alkyl is branched and contains 3 to 5 carbon atoms.

The succinic diesters and the nitriles are known compounds and can beprepared by known processes.

The amount of the nitrile used or the total amount of the nitriles usedought to be stoichiometric with respect to the amount of succinicdiester, in other words 2 mol of nitrile per mole of succinic diester.It has nevertheless proven advantageous to use an excess of nitrile orof succinic diester in order to obtain higher yields. Advantageously,relative to the stoichiometric amounts, excesses of nitrile or ofsuccinic diester of up to 10 times are used, preferably up to 5 times,in particular up to 3 times. Excess nitrile can be recovered.

The reaction of the succinic diester with the nitrile is carried out inan organic solvent. Examples of suitable solvents include primary,secondary or tertiary alcohols having 1 to 10 carbon atoms, such asmethanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,tert-butanol, pentanols, such as n-pentanol or 2-methyl-2-butanol,hexanol, such as 2-methyl-2-pentanol or 3-methyl-3-pentanol,2-methyl-2-hexanol, 3-ethyl-3-pentanol, octanols, such as2,4,4-trimethyl-2-pentanol, cyclohexanol, or glycols, such as ethyleneglycol, diethylene glycol, propylene glycol, dipropylene glycol orglycerol, or polyglycols, such as polyethylene glycols or polypropyleneglycols, ethers, such as methyl isobutyl ether, tetrahydrofuran,dimethoxyethane or dioxane, glycol ethers, such as monomethyl ormonoethyl ethers of ethylene glycol or of propylene glycol, diethyleneglycol monomethyl ether or diethylene glycol monoethyl ether, butylglycols or methoxybutanol, dipolar aprotic solvents, examples being acidamides such as dimethylformamide, N,N-dimethylacetamide orN-methylpyrrolidone, urea derivatives such as tetramethyl urea,aliphatic or aromatic hydrocarbons, such as cyclohexane or benzene oralkyl-, alkoxy-, nitro- or halogen-substituted benzene, such as toluene,xylenes, ethylbenzene, anisole, nitrobenzene, chlorobenzene,o-dichlorobenzene or 1,2,4-trichlorobenzene, aromatic N-heterocycles,such as pyridine, picoline or quinoline, and alsohexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide or sulfolane.

It is advantageous to use 2 to 25 parts by weight of solvent per part byweight of the reactants. The amount ought to be sufficient to ensure astirrable suspension. Moreover it is also possible to use the reactantnitrile of the formula (II) and/or (III) as a solvent at the same time,if it is liquid in the temperature range in which the reaction takesplace.

In the process of the invention it is preferred to use an alcohol assolvent, especially a secondary or tertiary alcohol. Preferred tertiaryalcohols are tert-butanol and tert-amyl alcohol.

It is also possible to use mixtures of the solvents, especially of thepreferred secondary and tertiary alcohols with aromatic hydrocarbons,such as toluene or xylene, or with halogen-substituted benzene, such aschlorobenzene.

The process of the invention is carried out in the presence of a strongbase. Suitable strong bases are, in particular, the alkali metalsthemselves, such as lithium, sodium or potassium, or alkali metalamides, such as lithium, sodium or potassium amide, or alkali metalhydrides, such as lithium, sodium or potassium hydride, or alkalineearth metal or alkali metal alkoxides, which derive in particular fromprimary, secondary or tertiary aliphatic alcohols having 1 to 10 carbonatoms, such as lithium, sodium or potassium methoxide, ethoxide,n-propoxide, isopropoxide, n-butoxide, sec-butoxide, tert-butoxide,2-methyl-2-butoxide, 2-methyl-2-pentoxide, 3-methyl-3-pentoxide and3-ethyl-3-pentoxide, for example. Mixtures of the stated bases can alsobe used.

In the process of the invention the strong base used preferablycomprises alkali metal alkoxides, where the alkali metal is sodium orpotassium in particular and the alkoxide derives preferably from asecondary or tertiary alcohol. Particularly preferred strong bases aretherefore, for example, sodium or potassium isopropoxide, sec-butoxide,tert-butoxide and tert-amyloxide. The alkali metal alkoxides can also beprepared in situ by reacting the corresponding alcohol with the alkalimetal, alkali metal hydride or alkali metal amide.

In the process of the invention the strong base can be used in an amountof 0.1 to 10 mol, preferably 1.9 to 5.0 mol, per mole of the reactantused in excess. Although stoichiometric amounts of base are sufficientin principle, an excess of base in many cases has an advantageous effecton the yield.

The inventive reaction of the succinic diester with the nitrites of theformula (II) or of the formula (III) is carried out in particular at atemperature of 60 to 200° C., preferably 80 to 140° C., undersuperatmospheric pressure if desired.

For the reaction the individual components can be added in any order,preferably at room temperature. It is also possible to introduce all ofthe components at a relatively low temperature and then to heat themixture into the range of the reaction temperature. One preferredembodiment which generally has a particularly advantageous effect on theyield is to introduce the reactant nitrile together with the base and tometer in the succinic diester in the region of the reaction temperature.Another possibility is to meter in the succinic diester and the reactantnitrile simultaneously to the initial charge of base at reactiontemperature. The process of the invention can be carried out batchwiseor continuously. Particularly in the case of succinic diesters withlower alkyl radicals and in the case of alkoxides deriving from loweralcohols, such as methanol, ethanol, n-propanol, isopropanol ortert-butanol, for example, it may prove necessary to remove the loweralcohol, formed in the course of the reaction, continually from thereaction medium in order to obtain higher yields. If the solvent used isan alcohol and the base used is an alkoxide, then it may be advantageousto choose an alcohol and an alkoxide having the same alkyl moieties. Itmay be equally advantageous for the succinic diester to contain the samekind of alkyl groups as well.

The hydrolysis agent used to hydrolyze the reaction product may comprisewater, one or more organic, protic solvents or one or more acids.Examples of suitable protic solvents include alcohols, preferably having1 to 4 carbon atoms, such as methanol or ethanol. Suitable acids includeorganic acids, such as aliphatic or aromatic carboxylic or sulfonicacids, examples being formic acid, acetic acid, propionic acid, butyricacid, hexanic acid, oxalic acid, citric acid, benzoic acid, phenylaceticacid, benzenesulfonic acid or p-toluenesulfonic acid, and inorganicacids, examples being hydrochloric acid, sulfuric acid or phosphoricacid. For the hydrolysis it is preferred to use an organic acid,particularly an aliphatic carboxylic acid, such as acetic acid andformic acid. It is also possible to use water, organic protic solventand/or acid in any combinations. The hydrolysis may also be carried outin the presence of organic aprotic solvents.

The hydrolysis may take place directly, by adding a hydrolysis agent tothe reaction suspension, or indirectly, by adding the reactionsuspension to the hydrolysis agent. The water, organic, protic solventand acid hydrolysis agents can be added and/or introduced as an initialcharge in any order and even as mixtures. The simultaneous addition ofindividual components to an initial charge is a further possibility: forexample, acid and the reaction suspension can be added simultaneously tothe initial charge of water and/or alcohol.

It may be advantageous to use a buffer during hydrolysis, such as aphosphate, acetate, citric acid or triethanolamine buffer, for example.

The temperature during the hydrolysis may be −20° C. to 200° C.,preferably −5 to 180° C., in particular 0 to 160° C., and the hydrolysistakes place under superatmospheric pressure if desired. Reactionsuspension and hydrolysis agent may also differ in temperature.Hydrolysis may also take place, for example, by means of steam.

The total amount of hydrolysis agent is advantageously an at leaststoichiometric amount relative to the base. For example, water and/or anorganic, protic solvent can be used at between 0.5 and 50 parts byweight per part of the pigment formed. The acid is employedadvantageously in a molar excess of from 0.1 to 10 times relative tobase. Where a water-containing suspension is present after thehydrolysis, the pH may be situated in the alkaline, in the neutral orelse in the acidic range.

Depending on the procedure the diketopyrrolopyrrole of the formula (I)is obtained in the course of the hydrolysis as a pigment, a finelydivided prepigment or a coarsely crystalline crude pigment. Pigmentspresent after the hydrolysis can be isolated in customary manner byfiltration. Prior to the isolation of the pigment the solvent may beremoved by distillation, where appropriate under reduced pressure, orelse by steam distillation. This may even take place during thehydrolysis.

Prepigments and crude pigments must be further subjected to anaftertreatment. For this purpose the hydrolysis suspension can be useddirectly, or alternatively the pigment can be isolated first and thenaftertreated.

The aftertreatment may comprise a thermal aftertreatment in water and/ororganic solvent at any pH and at a temperature of 50 to 250° C.,preferably from 80 to 190° C., under superatmospheric pressure ifdesired, for 10 minutes to 48 hours, preferably for 30 minutes to 8hours, or a grinding operation, or a combination of these twooperations.

Grinding may take place either by dry grinding or by wet grinding.

Mills suitable for dry grinding include all batch and continuousvibratory mills or roll mills, while suitable mills for wet grindinginclude all batch and continuous stirred ball mills, roll mills andvibratory mills and also kneading apparatus. Wet grinding takes place inwater and/or organic solvent at any pH.

It is preferred to carry out wet grinding with a high energy input, asfor example in a stirred ball mill with a power density of more than 1.0kW per liter of milling space and a peripheral stirrer speed of morethan 12 m/s. The hydrolysis agent or the reaction suspension may also beadded in portions and sequentially, so that between the individualportions there may be an intermediate treatment, such as a period ofprolonged stirring, for example, under elevated temperature if desired.For the aftertreatment it is preferred to use the hydrolysis suspension,without isolation of the diketopyrrolopyrrole beforehand.

In order to enhance the coloristic properties and to achieve certainperformance effects it is possible to use auxiliaries such assurfactants, pigmentary and nonpigmentary dispersants, fillers,standardizers, resins, waxes, defoamers, antidust agents, extenders,shading colorants, preservatives, drying retarders, rheology controladditives, wetting agents, antioxidants, UV absorbers, light stabilizersor a combination thereof.

Auxiliaries can be added at any desired point in time before, during orafter the reaction, hydrolysis and/or aftertreatment, all at once or intwo or more portions. The total amount of the added auxiliaries mayamount to 0 to 40% by weight, preferably 1 to 30% by weight, morepreferably 2.5 to 25% by weight, based on the diketopyrrolopyrrolepigment.

Suitable surfactants include anionic or anion-active, cationic orcation-active, and nonionic substances or mixtures of these agents.Preferred surfactants or surfactant mixtures are those which do notfoam.

Examples of suitable anionic substances include fatty acid taurides,fatty acid N-methyltaurides, fatty acid isethionates,alkylphenylsulfonates, alkylnaphthalenesulfonates, alkylphenolpolyglycol ether sulfates, fatty alcohol polyglycol ether sulfates,fatty acid amide polyglycol ether sulfates, alkylsulfosuccinamates,alkenylsuccinic monoesters, fatty alcohol polyglycol ethersulfosuccinates, alkanesulfonates, fatty acid glutamates,alkylsulfosuccinates, fatty acid sarcosides; fatty acids, examples beingpalmitic, stearic and oleic acid; soaps, examples being alkali metalsalts of fatty acids, naphthenic acids and resin acids, such as abieticacid, alkali-soluble resins, examples being rosin-modified maleateresins and condensation products based on cyanuric chloride, taurine,N,N′-diethylaminopropylamine and p-phenylenediamine. Particularpreference is given to resin soaps, i.e., alkali metal salts of resinacids.

Examples of suitable cationic substances include quaternary ammoniumsalts, fatty amine alkoxylates, alkoxylated polyamines, fatty aminepolyglycol ethers, fatty amines, diamines and polyamines derived fromfatty amines or fatty alcohols, and the alkoxylates of said amines,imidazolines derived from fatty acids, and salts of these cationicsubstances, such as acetates, for example.

Examples of suitable nonionic substances include amine oxides, fattyalcohol polyglycol ethers, fatty acid polyglycol esters, betaines, suchas fatty acid amide N-propyl betaines, phosphoric esters of aliphaticand aromatic alcohols, fatty alcohols or fatty alcohol polyglycolethers, fatty acid amide ethoxylates, fatty alcohol-alkylene oxideadducts and alkylphenol polyglycol ethers.

By nonpigmentary dispersants are meant substances which in structuralterms are not derived from organic pigments by chemical modification.They are added as dispersants either during the actual preparation ofpigments or else in many cases during the incorporation of the pigmentsinto the application media to be colored: for example, during thepreparation of paints or printing inks by dispersing of the pigmentsinto the corresponding binders. They may be polymeric substances, suchas polyolefins, polyesters, polyethers, polyamides, polyimines,polyacrylates, polyisocyanates, block copolymers thereof, copolymers ofthe corresponding monomers or polymers of one class modified with a fewmonomers of a different class. These polymeric substances carry polaranchor groups such as hydroxyl, amino, imino and ammonium groups,carboxylic acid and carboxylate groups, sulfonic acid and sulfonategroups or phosphonic acid and phosphonate groups, for example, and canalso be modified with aromatic nonpigmentary substances. Nonpigmentarydispersants may additionally be aromatic substances modified chemicallywith functional groups but not derived from organic pigments.Nonpigmentary dispersants of this kind are known to the skilled workerand in some cases are available commercially (e.g., Solsperse®, Avecia;Disperbyk®, Byk, Efka®, Efka). A number of types will be mentioned belowas representatives; however, it is possible in principle to use anydesired other substances described, examples being condensation productsof isocyanates and alcohols, diols or polyols, amino alcohols ordiamines or polyamines, polymers of hydroxycarboxylic acids, copolymersof olefin monomers or vinyl monomers and ethylenically unsaturatedcarboxylic acids and esters, urethane-containing polymers ofethylenically unsaturated monomers, urethane-modified polyesters,condensation products based on cyanuric halides, polymers containingnitroxyl compounds, polyesteramides, modified polyamides, modifiedacrylic polymers, comb dispersants formed from polyesters and acrylicpolymers, phosphoric esters, polymers derived from triazine, modifiedpolyethers, or dispersants derived from aromatic, nonpigmentarysubstances. These base structures are in many cases modified further, bymeans for example of chemical reaction with further substances whichcarry functional groups, or by formation of salts.

By pigmentary dispersants are meant pigment dispersants which derivefrom an organic pigment as base structure and are prepared by chemicalmodification of said base structure; examples includesaccharine-containing pigment dispersants, piperidyl-containing pigmentdispersants, naphthalene- or perylene-derived pigment dispersants,pigment dispersants containing functional groups linked to the pigmentbase structure via a methylene group, pigment base structures modifiedchemically with polymers, pigment dispersants containing sulfo acidgroups, sulfonamide groups or sulfo acid ester groups, pigmentdispersants containing ether or thioether groups, or pigment dispersantscontaining carboxylic acid, carboxylic ester or carboxamide groups.

Mixtures of compounds of the formula (I) can also be prepared by jointhydrolysis of different reaction solutions prepared independently of oneanother, with or without mixing the reaction solutions beforehand, orelse by joint reprecipitation of two or more compounds of the formula(I).

Asymmetrically substituted diketopyrrolopyrroles of the formula (I) canalso be prepared by reacting not a nitrile with succinic diester butinstead an ester of the formula (IV) or of the formula (V),

with a nitrile of the formula (III) in an organic solvent in thepresence of a strong base with subsequent hydrolysis, R¹ and R² havingthe stated definition and R⁵ and R⁶ being an unsubstituted orsubstituted alkyl or aryl radical, preferably the ester radicalsspecified in connection with the succinic diesters.

This reaction can be carried out in analogy to the conditions describedfor the reaction of succinic diesters with nitrile.

The esters of the formula (IV) and of the formula (V) can be prepared inanalogy to the processes disclosed in US-B1-6,207,697 or WO 00/34248.

The diketopyrrolopyrrole pigments of the invention can be employed aspreferably aqueous presscakes, but generally comprise solids systems offree-flowing powderlike nature, or granules.

The diketopyrrolopyrrole pigments of the invention are notableparticularly in coating materials for outstanding coloristic andrheological properties, and in particular for outstanding rheology, hightransparency, effective gloss, high color strength, flawless overcoatingfastnesses and very effective light fastness and weather fastness. Theycan be used in solventborne and in aqueous systems. In plastics andprinting systems, too, they exhibit good properties and can therefore beused universally.

The diketopyrrolopyrrole pigments prepared in accordance with theinvention can be used for pigmenting high molecular mass organicmaterials of natural or synthetic origin, such as plastics, resins,varnishes, paints or electrophotographic toners and developers, and alsodrawing, writing and printing inks, for example.

Examples of high molecular mass organic materials that can be pigmentedwith the stated pigments include cellulose ethers and cellulose esters,such as ethylcellulose, nitrocellulose, cellulose acetate or cellulosebutyrate, natural resins or synthetic resins, such asaddition-polymerization resins or condensation resins, examples beingamino resins, especially urea-formaldehyde and melamine-formaldehyderesins, alkyd resins, acrylic resins, phenolic resins, polycarbonates,polyolefins, such as polystyrene, polyvinyl chloride, polyethylene,polypropylene, polyacrylonitrile, polyacrylic esters, polyamides,polyurethanes or polyesters, rubber, casein, silicone and siliconeresins, individually or in mixtures.

It is irrelevant whether the aforementioned high molecular mass organiccompounds are in the form of plastic masses, melts or in the form ofspinning solutions, varnishes, paints or printing inks. Depending on theintended use it is found advantageous to utilize the pigments obtainedin accordance with the invention in the form of a blend or in the formof preparations or dispersions. Based on the high molecular mass organicmaterial to be pigmented, the pigments of the invention are used in anamount of from 0.05 to 30% by weight, preferably 0.1 to 15% by weight.

The pigments of the invention are also suitable for use as colorants inelectrophotographic toners and developers, such as one- or two-componentpowder toners (also called one- or two-component developers), magnetictoners, liquid toners, polymerization toners and specialty toners, forexample.

Typical toner binders are addition-polymerization resins, polyadditionresins and polycondensation resins, such as styrene, styrene-acrylate,styrene-butadiene, acrylate, polyester and phenol-epoxy resins,polysulfones, polyurethanes, individually or in combination, and alsopolyethylene and polypropylene, which may already include, or bemodified subsequently with, further ingredient additions, such as chargecontrol agents, waxes or flow assistants.

The pigments of the invention are further suited to use as colorants inpowders and powder coating materials, particularly in triboelectricallyor electrokinetically sprayable powder coating materials which areemployed to coat the surfaces of articles made, for example, from metal,wood, plastic, glass, ceramic, concrete, textile material, paper orrubber.

Resins used as powder coating resins are typically epoxy resins,carboxyl- and hydroxyl-containing polyester resins, polyurethane resinsand acrylic resins, together with customary curatives. Resincombinations also find use. Thus, for example, epoxy resins arefrequently employed in combination with carboxyl- andhydroxyl-containing polyester resins. Typical curative components(depending on the resin system) are, for example, acid anhydrides,imidazoles and also dicyandiamide and its derivatives, blockedisocyanates, bisacylurethanes, phenolic and melamine resins, triglycidylisocyanurates, oxazolines and dicarboxylic acids.

The pigments of the invention are also suitable for use as colorants inink-jet inks, on both an aqueous and a nonaqueous basis, and also inthose inks which operate in accordance with the hot-melt process.

Ink-jet inks generally contain a total of from 0.5 to 15% by weight,preferably 1.5 to 8% by weight, (calculated on a dry basis) of one ormore of the compounds prepared in accordance with the invention.

Microemulsion inks are based on organic solvents, water and, if desired,an additional hydrotropic substance (interface mediator).

Microemulsion inks generally contain 0.5 to 15% by weight, preferably1.5 to 8% by weight, of one of more of the compounds prepared inaccordance with the invention, 5 to 99% by weight of water and 0.5 to94.5% by weight of organic solvent and/or hydrotropic compound.

Solvent-based ink-jet inks contain preferably 0.5 to 15% by weight ofone or more compounds prepared in accordance with the invention, 85 to99.5% by weight of organic solvent and/or hydrotropic compounds.

Hot-melt inks are generally based on waxes, fatty acids, fatty alcoholsor sulfonamides which are solid at room temperature and become liquid onheating, the preferred melting range being situated between about 60° C.and about 140° C. Hot-melt ink-jet inks are composed essentially, forexample, of 20 to 90% by weight of waxes and 1 to 10% by weight of oneor more of the compounds prepared in accordance with the invention.Additionally it is possible for them to contain from 0 to 20% by weightof an additional polymer (as “dye dissolver”), 0 to 5% by weight ofdispersing assistant, 0 to 20% by weight of viscosity modifier, 0 to 20%by weight of plasticizer, 0 to 10% by weight of tack additive, 0 to 10%by weight of transparency stabilizer (which prevents, for example,crystallization of the waxes) and 0 to 2% by weight of antioxidant.Typical additives and auxiliaries are described for example in U.S. Pat.No. 5,560,760.

Additionally the pigments of the invention are also suitable for use ascolorants for color filters, for both additive and subtractive colorgeneration, and also for electronic inks.

To assess the properties of the pigments in the plastics field aselection was made, from among the multiplicity of known plastics, ofplasticized polyvinyl chloride (PVC).

To assess the properties of the pigments in the printing sector aselection was made, from among the multiplicity of known printingsystems, of a gravure printing system based on nitrocellulose (NC).

To assess the properties of the pigments in the coatings sector aselection was made, from among the multiplicity of known varnishes, of ahigh-solids acrylic resin stoving varnish based on a nonaqueousdispersion (HS), of an aqueous varnish based on polyurethane (PU), andof an alkyd-melamine resin varnish (AM) based on a medium-oil alkydresin and on a butanol-etherified melamine resin.

The color strength and hue were determined in accordance with DIN 55986.The millbase rheology after dispersion was evaluated visually on thebasis of the following five-point scale:

-   5 highly fluid-   4 liquid-   3 viscous-   2 slightly set-   1 set

The overcoating fastness was determined in accordance with DIN 53221.

The viscosity was determined, following dilution of the millbase to thefinal pigment concentration, using the Rossmann viscospatula type 301from Erichsen.

In the examples below, parts and percentages are by weight in each case.

EXAMPLE 1a

A four-necked flask is charged with 252.8 parts of tert-amyl alcohol,anhydrous. Following the introduction of 23 parts of sodium the mixtureis stirred under reflux until the sodium has reacted. At 100° C. 58.6parts of the nitrile of the formula (XX)

are introduced. Over the course of 2 hours 30.4 parts of diisopropylsuccinate are added dropwise at 100° C. Then the mixture is stirredunder reflux for 4 hours. After the reaction suspension has cooled to80° C. it is poured into a mixture of 300 parts of water and 400 partsof methanol at 25° C. The hydrolysis suspension is stirred under refluxfor 6.5 hours. After it is cooled to room temperature, 320 parts ofmethanol are added and stirred in, and then the suspension is filteredand the pigment is washed with methanol. The presscake is suspended in1280 parts of methanol and stirred in, the suspension is filtered andthe pigment is washed with methanol and water and dried at 80° C.

This gives 36.6 parts of diketopyrrolopyrrole pigment of the formula(XXI).

In the HS varnish the pigment provides transparent coatings with astrong, clean, orange hue and flawless overcoating fastness. Themetallic finish is bright with a strong golden-yellow hue. In the PUvarnish bright metallic finishes with a strong golden yellow hue areobtained; the rheology is very good and is rated 5.

EXAMPLE 1b (COMPARATIVE EXAMPLE)

The diketopyrrolopyrrole of the formula (XXII) was prepared inaccordance with EP 94911, example 12, and compared against thediketopyrrolopyrrole of the formula (XXI) prepared in accordance withexample 1a. In the HS varnish the coatings are significantly more hidingand weaker in color, with a brownish red hue which is substantially moreturbid. The weather fastness is also poorer. In the PU varnish therheology is rated only at 2 to 3.

EXAMPLE 1c (COMPARATIVE EXAMPLE)

The diketopyrrolopyrrole of the formula (XXIII) was prepared inaccordance with EP 94911, example 14, and compared against thediketopyrrolopyrrole of the formula (XXI) prepared according to example1a. In the HS varnish the coatings are substantially more hiding andhave a brownish violet hue which is substantially more turbid. Themetallic coating is weak in color with a gray-brown hue. In the PUvarnish as well a similar, markedly inferior coloristic quality isobtained.

EXAMPLE 2

A four-necked flask is charged with 189.6 parts of tert-amyl alcohol,anhydrous. Following the introduction of 17.3 parts of sodium themixture is stirred under reflux until the sodium has reacted. At 100° C.41.9 parts of the nitrile of the formula (XXIV)

are introduced. Over the course of 2 hours 22.8 parts of diisopropylsuccinate are added dropwise at 100° C. Then the mixture is stirredunder reflux for 4 hours. After the reaction suspension has cooled to80° C. it is poured into a mixture of 225 parts of water and 300 partsof methanol at 25° C. The hydrolysis suspension is stirred under refluxfor 6.5 hours. After it is cooled to room temperature, 240 parts ofmethanol are added and stirred in, and then the suspension is filteredand the pigment is washed with methanol. The presscake is suspended in960 parts of methanol and stirred in, the suspension is filtered and thepigment is washed with methanol and water and dried at 80° C.

This gives 26.8 parts of diketopyrrolopyrrole pigment of the formula(XXV).

In the HS varnish the pigment provides transparent coatings with aclean, orange hue and flawless overcoating fastness.

EXAMPLE 3

A four-necked flask is charged with 189.6 parts of tert-amyl alcohol,anhydrous. Following the introduction of 17.3 parts of sodium themixture is stirred under reflux until the sodium has reacted. At 100° C.5 parts of the nitrile of the formula (XXIV) and 38.6 parts of thenitrile of the formula (XX) are introduced. In 2 hours 22.8 parts ofdiisopropyl succinate are added dropwise at 100° C. Then the mixture isstirred under reflux for 4 hours. After the reaction suspension hascooled to 80° C. it is poured into a mixture of 225 parts of water and300 parts of methanol at 25° C. The hydrolysis suspension is stirredunder reflux for 2 hours. After it has cooled to room temperature 240parts of methanol are added and stirred in and then the suspension isfiltered and the pigment is washed with methanol. The presscake issuspended in 960 parts of methanol and stirred in, the suspension isfiltered and the pigment is washed with methanol and water and dried at80° C. This gives 25.9 parts of diketopyrrolopyrrole pigment composed ofa mixture of pigments of the formula (XXI), (XXV) and (XXVI).

In the PU varnish the pigment produces transparent coatings with aclaret hue and flawless overcoating fastness. In contrast to this acommercially customary pigment P.R.255, prepared in accordance with theprocess disclosed in EP 94911, exhibits an inadequate overcoatingfastness in the PU varnish.

EXAMPLE 4

A four-necked flask is charged with 176 parts of tert-amyl alcohol,anhydrous. Following the introduction of 13.8 parts of sodium themixture is stirred under reflux until the sodium has reacted. At 100° C.39.5 parts of the nitrile of the formula (XXVII)

are introduced. Over the course of 5 hours at 100° C. 22.7 parts ofdiisopropyl succinate are added dropwise. Then the mixture is stirredunder reflux for 1 hour. After the reaction suspension has cooled to 80°C. it is poured into 430 parts of water at 40° C. The hydrolysissuspension is stirred under reflux for 4.5 hours. After it has cooled toroom temperature 670 parts of methanol are added and stirred in and thenthe suspension is filtered and the pigment is washed with methanol andwater and dried at 80° C.

This gives 32.8 parts of diketopyrrolopyrrole pigment of the formula(XXVIII).

In the AM varnish the pigment produces opaque coatings with a strongyellowish-red hue and flawless overcoating fastness; the viscosityamounts to 3 sec. In PVC, strong colorations with an orange hue, and inthe NC print strong colorations with a yellowish-red hue, are obtained.

1. A diketopyrrolopyrrole of the formula (I)

wherein R¹, R², R³ and R⁴ independently of one another are a C₁–C₄ alkylradical or a substituted or unsubstituted phenyl radical, wherein thesubstituted phenyl radical is substituted by 1, 2, 3 or 4 substituentsselected from the group consisting of C₁–C₄ alkyl, C₁–C₄ alkoxy, CN, F,Cl, Br, NO₂, CF₃, S—C₁–C₄ alkyl, phenyl and (C₁–C₂)alkylenephenyl, withthe proviso that at least one of the radicals, R¹, R², R³, or R⁴, is asubstituted or unsubstituted phenyl radical.
 2. A diketopyrrolopyrroleas claimed in claim 1, wherein the radicals R¹ and R⁴ are identical andthe radicals R² and R³ are identical.
 3. A diketopyrrolopyrrole asclaimed in claim 1, wherein the radicals R¹, R², R³ and R⁴ independentlyof one another are methyl, ethyl, phenyl or phenyl substituted by 1 or 2substituents selected from the group consisting of methyl, ethyl,methoxy, ethoxy, CN, F, Cl, S-methyl, phenyl and benzyl.
 4. Adiketopyrrolopyrrole as claimed in claim 1, wherein R¹ and R⁴ are each amethyl or ethyl group and R² and R³ are each an identical phenyl radicalwhich is unsubstituted or substituted by 1 or 2 substituents selectedfrom the group consisting of methyl, ethyl, methoxy, ethoxy, F, Cl, NO₂,CF₃, phenyl and benzyl.
 5. A mixture of two or morediketopyrrolopyrroles as claimed in claim
 1. 6. A process for preparinga diketopyrrolopyrrole as claimed in claim 1, comprising the steps ofreacting a succinic diester with a nitrile of the formula (II) (III), orwith a mixture of 2, 3 or 4 different nitriles of the formula (II) or(III),

in an organic solvent in the presence of a strong base and subsequentlyhydrolyzing.
 7. A process for preparing a diketopyrrolopyrrole of theformula (I) as claimed in claim 1, comprising the steps of reacting anester of the formulae (IV) or (V)

in which R⁵ and R⁶ are an unsubstituted or substituted alkyl or arylradical, with a nitrile of the formula (III)

in an organic solvent in the presence of a strong base and subsequentlyhydrolyzing.
 8. A pigmented high molecular mass organic material ofnatural or synthetic origin pigmented with at least onediketopyrrolopyrrole as claimed in claim
 1. 9. The pigmented highmolecular mass organic material as claimed in claim 8, wherein thepigmented high molecular mass material is an ink-jet ink.
 10. A compoundof the formula (IV)

wherein R⁵ and R⁶ are an unsubstituted or substituted alkyl or arylradical and R¹ and R² independently of one another are a C₁–C₄ alkylradical or a substituted or substituted phenyl radical, wherein theunsubstituted phenyl radical is substituted by 1, 2, 3 or 4 substituentsselected from the group consisting of C₁–C₄ alkyl, C₁–C₄ alkoxy, CN, F,Cl, Br, NO₂, CF₃, S—C₁–C₄ alkyl, phenyl and (C₁–C₂)alkylenephenyl, withthe proviso that at least one of the radicals, R¹ and R² is asubstituted or unsubstituted phenyl radical.
 11. The pigmented highmolecular mass organic material as claimed in claim 8, wherein thepigmented high molecular mass material is selected from the groupconsisting of plastics, resins, varnishes, paints, electrophotographictoners, electrophotographic developers, color filters, drawing inks,writing inks and printing inks.
 12. A compound of the formula (V)

wherein R⁵ is an unsubstituted or substituted alkyl or aryl radical andR¹ and R² independently of one another are a C₁–C₄ alkyl radical or asubstituted or substituted phenyl radical, wherein the unsubstitutedphenyl radical is substituted by 1, 2, 3 or 4 substituents selected fromthe group consisting of C₁–C₄ alkyl, C₁–C₄ alkoxy, CN, F, Cl, Br, NO₂,CF₃, S—C₁–C₄ alkyl, phenyl and (C₁–C₂)alkylenephenyl, with the provisothat at least one of the radicals, R¹ and R² is a substituted orunsubstituted phenyl radical.